Bi-directional clutch unit

ABSTRACT

A clutch unit has an oil pump which is powered by the input shaft and an oil pump which is powered by the output shaft. The oil pump powered by the input shaft pumps oil in both a clockwise and counterclockwise rotation of the input shaft. The oil flow is controlled by a unique bi-directional check valve which automatically selects the passage through which oil is being pumped. The oil pump powered by the output shaft provides oil to the friction plates of the clutch only when the clutch is engaged.

FIELD OF THE INVENTION

The present invention relates to drive units incorporating a clutch.More particularly, the present invention relates to a self-containedhydraulic clutch unit that can be driven in either a clockwise or acounterclockwise direction.

BACKGROUND OF THE INVENTION

Oil shear brake and clutch units have been developed to eliminate theproblems associated with the dry friction type of units. Properlydesigned oil shear clutch or brake drives offer the advantage of littleor no wear of the friction plates in the disk stacks and no fading.These oil shear units thus provide a more precise operation of themachine tool and dramatically increase the machine tool's up-time. Theoil film between the adjacent friction plates carries the heat generatedby the starting and stopping of the machine tool away from the frictionplate stacks. This removal of heat offers the advantage that there isnow no practical limit in the disengage/engage rate or in the speed ofthe input device.

Oil shear clutch units are utilized to intermittently transferrotational power from a continuously rotating input shaft to an outputshaft. The output shaft is connected to the input of a machine tool. Theclutch unit is normally operating in a disengaged condition. The inputshaft is rotating with respect to the output shaft and there is no powerbeing transmitted through the clutch unit. When a control system gives acommand to operate the machine tool, the clutch unit is engaged to lockthe input shaft to the output shaft and transmit power through theclutch unit.

Typical clutch units can be engaged electrically, pneumatically orhydraulically. The; choice of an electric clutch versus a pneumaticclutch versus a hydraulic clutch is sometimes determined by theavailability of electrical, pneumatic or hydraulic power and sometimesthe design choice for the brake unit, is dictated by the application ormachine tool to which it is being mated. When the driving torques orpower being transferred through the clutch unit increase, electricaloperation of the clutch is no longer a viable option. This is due to theclamping loads required between the friction plates and the requiredelectrical components needed to generate these loads. Thus, higher powerclutch units are typically pneumatically or hydraulically actuated.

When considering the choice between pneumatic and hydraulic operation ofthe clutch, the choice can be dictated by the availability of a sourceof compressed air or a source of pressurized hydraulic oil. Whenconsidering compressed air as the actuating medium, the lower thepressure of the available compressed air, the larger the area for thepiston which generates the required load. Thus, unless a high pressuredair source is readily available, the choice for the design of the higherpowered clutch unit will be hydraulic actuation.

When considering hydraulic actuation, the source of the pressurizedhydraulic fluid can be external to the clutch unit or the clutch unitcan incorporate an oil pump which supplies the necessary pressurizedhydraulic fluid. For oil shear clutch units, the integration of the oilpump into the clutch unit allows for the sharing of an oil sump becausethe oil shear clutch units typically include an oil sump for lubricatingbearings, friction plates and other moving components.

One consideration when developing clutch units with integratedpressurized hydraulic fluid supplies is the direction of rotation of theclutch unit. Typically oil pumps are unidirectional and thusconsideration must be given to the direction of rotation. Preferably, aclutch unit should be designed to operate in both a clockwise directionand a counterclockwise direction with minimal changes to the clutch unitin order to properly function in either direction.

Thus, the continued development of clutch units have been thedevelopment of hydraulic fluid management systems which allow theoperation of the clutch unit in both rotational directions withouthaving to manually adapt the clutch unit.

SUMMARY OF THE INVENTION

The present invention provides the art with a clutch unit thatautomatically adjusts the hydraulic fluid flow based upon the rotationaldirection of the input shaft. The clutch unit incorporates a gear pumphaving two outlets, one for each direction of rotation. The two outletseach lead to a separate fluid supply passage and these two fluid supplypassages combine to feed a fluid passage leading to an actuation valve.A check valve is disposed between the two supply passages toautomatically close the supply passage not being used thus prohibitingfluid flow back to the oil sump. The clutch unit also includes a secondoil pump which pumps hydraulic fluid to the friction surfaces of thefriction plates. The second oil pump is bi-directional and it isattached to the output shaft such that it is active only when the clutchunit is engaged.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a vertical cross-sectional view of the clutch unit inaccordance with the present invention;

FIG. 2 is a top plan view illustrating the hydraulic control system forthe clutch unit shown in FIG. 1; and

FIG. 3 is an end cross-sectional view of the clutch unit in thedirection of arrow 3—3 shown in FIG. 1 illustrating the pressurizedhydraulic pump in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

Referring now to the drawings in which like reference numerals designatelike or corresponding parts throughout the several views, there is shownin FIGS. 1 through 3 a clutch unit in accordance with the presentinvention and which is designated generally by the reference numeral 10.Clutch unit 10 comprises a main housing 12, a fan housing 14, anactuation assembly 16, an input shaft 18, an output shaft 20, a clutchassembly 22 and a control block assembly 24.

Main housing 12 defines a chamber 30 which is filled to a specifiedlevel with hydraulic fluid. The hydraulic fluid within chamber 30lubricates all of the moving components of clutch unit 10 as well asproviding the hydraulic fluid for engaging clutch unit 10 as is detailedbelow. Main housing 12 also defines a cavity 32 within which is mounteda bearing 34. Bearing 34 rotatably supports input shaft 18 as detailedbelow.

Fan housing 14 is secured to one side of main housing 12 utilizing aplurality of bolts. Fan housing 14 defines a pair of intersectingcircular pockets 36 and 38 within which a gear pump 40 is located. Gearpump 40 includes a driving gear 42 driven by input shaft 18 and a drivengear 44 rotatably supported on a bearing pin 46. Fan housing 14 definesa cavity 48 within which is mounted a bearing 50. Bearing 50 rotatablysupports input shaft 18 as detailed below. A bearing retainer 52 isbolted to fan housing 14 to retain bearing 50 and a seal 54 is locatedbetween bearing retainer 52 and input shaft 18 to seal chamber 30. Fanhousing 14 defines a fan chamber 56 within which is located a fan 58.Fan 58 is driven by input shaft 18 and operates to blow air around andover clutch unit 10 through a number of ports 60 in order to cool clutchunit 10.

Actuation assembly 16 is secured to the opposite side of main housing 12utilizing a plurality of bolts. Actuation assembly 16 comprises an inputhousing 62, a bearing housing 64 and a piston 66. Input housing 62 isbolted to main housing 12 utilizing a plurality of bolts. Input housing62 defines a fluid passage 68 extending radially through input housing62. Fluid passage 68 is utilized for the engagement of clutch unit 10 asdetailed below. Bearing housing 64 is bolted to input housing 62 and itdefines a cavity 70 within which is mounted a bearing 72. Bearing 72rotatably supports output shaft 20 as detailed below. A bearing retainer74 is bolted to bearing housing 64 to retain bearing 72 and a seal 76 islocated between bearing retainer 74 and output shaft 20 to seal chamber30. Input housing 62 and bearing housing 64 define an annular fluidchamber 78 which is in communication with fluid passage 68. Piston 66 isslidingly disposed within fluid chamber 78. A plurality of springs 80urge piston 66 into fluid chamber 78 or to the right as shown in FIG. 1.In this position, clutch unit 10 is disengaged. When it is desired toengage clutch unit 10, a pressurized fluid is supplied to fluid chamber78 through fluid passage 68. The pressurized fluid reacts against piston66 urging piston 66 out of fluid chamber 78 against the load exerted bysprings 80 or to the left as shown in FIG. 1. In this position, clutchunit 10 is engaged.

Input shaft 18 extends through fan housing 14 and main housing 12 intochamber 30. Input shaft 18 is rotatably supported by bearings 34 and 50and input shaft 18 powers fan 58 and gear pump 40. The end of inputshaft 18 which extends into chamber 30 defines a cavity 82 within whichclutch assembly 22 and the inner end of output shaft 20 are located.

Output shaft 20 extends through actuation assembly 16 into chamber 30and into cavity 82. Output shaft 20 is rotatably supported by bearing72. The end of output shaft 20 which extends into cavity 82 is adaptedto support clutch assembly 22 as detailed below. Output shaft 20 definesa cavity 84 within which is mounted a bearing 86. Bearing 86 is locatedbetween output shaft 20 and a bearing mount 88 secured to input shaft18. Thus, bearing 86 rotatably supports output shaft 20 with respect toinput shaft 18.

Clutch assembly 22 comprises a plurality of driving friction plates 90,a plurality of driven friction plates 92, an abutment member 94 and anengagement member 96. The plurality of driving friction plates 90 areattached to input shaft 18 using a spline 98 located on input shaft 18which mates with a spline 100 located on the outer circumference ofdriving friction plates 90. Splines 98 and 100 locate the plurality ofdriving friction plates 90 within cavity 82 such that rotation withrespect to input shaft 18 is prohibited but driving friction plates 90are allowed to move axially within cavity 82. The plurality of drivingfriction plates thus rotate with input shaft 18. Interjected orinterleaved between the plurality of driving friction plates 90 are theplurality of driven plates 92. The plurality of driven plates 92 includea spline 102 on their interior circumference which mates with a spline104 located on output shaft 20. Splines 102 and 104 locate the pluralityof driven friction plates 92 within cavity 82 such that rotation withrespect to output shaft 20 is prohibited but driven friction plates 92are allowed to move axially within cavity 82. The plurality of drivenfriction plates thus rotate with output shaft 20.

The plurality of driving friction platets 90 and the plurality of drivenfriction plates 92 are located between abutment member 94 and engagementmember 96. Abutment member 94 is an annular ring bolted to input shaft18. Abutment member 94 provides an annular surface against which thecompression of friction plates 90 and 92 react. Engagement member 96 isan annular member defining an outer circumferential spline 106. Spline106 engages with spines 98 of input shaft 18. Splines 98 and 106 locateengagement member 96 within cavity 82 such that rotation with respect toinput shaft 18 is prohibited but engagement member 96 is allowed to moveaxially within cavity 82. Thus, engagement member 96 rotates with inputshaft 18.

A bearing 108 is disposed between engagement member 96 and piston 66.Bearing 108 allows rotation of engagement member 96 with respect topiston 66 and also allows axial movement of piston 66 to be transferredto engagement member 96 to provide axial movement of engagement member96 and the associated engagement and disengagement of clutch unit 10.

A centrifugal oil pump 110 is attached to output shaft 20 using aplurality of bolts. Oil pump 110 defines at least one cavity 112 whichreceives oil from the oil sump in chamber 30. The oil level in chamber30 is designed to be above the lowest portion of centrifugal oil pump110. Thus, when output shaft 20 rotates, each of the cavities 112becomes immersed in hydraulic oil to fill the cavity. The hydraulic oilwithin cavities 112 is forced by centrifugal force through an associatedaxial passage 114 extending through output shaft 20 and then radiallyoutward through a plurality of radial passages 116 extending frompassage 114 through output shaft 20. In this way, hydraulic oil iscentrifugally pumped from passages 116 to a position in between frictionplates 90 and 92 to remove heat generated by the friction generatedduring engagement and disengagement of clutch unit 10. The pumping ofhydraulic oil to the radial inner interface between friction plates 90and 92 occurs only when clutch unit 10 is engaged or only when outputshaft 20 is rotating.

Control block assembly 24 comprises a valve block 120, a pressure reliefvalve 122, a solenoid valve 124 and a pressure gauge 126. Valve block120 is secured to main housing 12 using a plurality of bolts. Theattachment of valve block 120 to main housing 12 closes chamber 30.Valve block 120 defines a fluid passage 128 which receives pressurizedhydraulic fluid from gear pump 40. Pressure gauge 126 is incommunication with fluid passage 128 and it provides a direct reading ofthe fluid pressure within fluid passage 128.

Fluid passage 128 has two outlet passages 130 and 132. Outlet passage130 is in communication with chamber 30. Pressure relief valve 122 isdisposed between fluid passage 128 and outlet passage 130 in order tocontrol the fluid pressure within passage 128. Pressure relief valve 122is an adjustable relief valve which will open a communication pathbetween passage 128 and passage 130 when a specific fluid pressure isreached. Pressure gauge 126 is utilized to indicate the pressure settingfor pressure relief valve 122.

Outlet passage 132 is in communication with fluid passage 68 extendingthrough input housing 62 and thus outlet passage 132 is in communicationwith annular fluid chamber 78. A fluid line 134 extends between passage132 and passage 68. Solenoid valve 124 is disposed between fluid passage128 and outlet passage 132 in order to control the fluid pressure withinannular fluid chamber 78. When it is desired to engage clutch unit 10,solenoid valve 124 is actuated to open communication between passages132 and 68 through fluid line 134 to provide pressurized hydraulic fluidto annular fluid chamber 78. A return passage 136 extends betweensolenoid valve 124 and chamber 30 to allow the return of fluid tochamber 30 from annular fluid chamber 78 when solenoid valve 124 isdeactuated.

Referring now to FIG. 3, gear pump 40 is illustrated. Gear pump 40includes driving gear 42 disposed within pocket 38 in mesh with drivengear 44 disposed within pocket 36. The depth of hydraulic oil withinchamber 30 is sufficient to ensure that driven gear 44 will be at leastpartially submerged in hydraulic oil. At the two overlapping sections ofpockets 36 and 38, are a clockwise outlet 140 and a counterclockwiseoutlet 142. Clockwise outlet 140 is in communication with a clockwisefluid passage 144 which is in turn in communication with a fluid outlet146. Fluid outlet 146 is in communication with fluid passage 128 ofvalve block 120. Counterclockwise outlet 142 is in communication with acounterclockwise fluid passage 148 which is in turn in communicationwith fluid outlet 146. A bi-directional check valve 150 is disposed atthe intersection of passages 144, 148 and outlet 146.

Bi-directional check valve 150 includes a clockwise fitting 152, acounterclockwise fitting 154 and a check ball 156. When input shaft 18is rotating in a clockwise direction, oil from chamber 30 is picked upby driven gear 44 and is subsequently forced or pumped through clockwiseoutlet 140 and into clockwise fluid passage 144 by the meshing ofdriving gear 42 with driven gear 44. Oil pumped through passage 144pushes check ball 156 against counterclockwise fitting 154 and the oilis therefore pumped through fluid outlet 146 and into fluid passage 128of valve block 120. In a similar manner, when input shaft 18 is rotatingin a counterclockwise direction, oil from chamber 30 is picked up bydriven gear 44 and is subsequently forced or pumped throughcounterclockwise outlet 142 and into counterclockwise fluid passage 148by the meshing of driving gear 42 with driven gear 44. Oil pumpedthrough passage 148 pushes check ball 156 against clockwise fitting 152and the oil is therefore pumped through fluid outlet 146 and into fluidpassage 128 of valve block 120. Thus, the incorporation ofbi-directional check valve 150 in conjunction with gear pump 40 providesan extremely efficient method for allowing the use of clutch drive 10 inboth clockwise and counterclockwise applications without the need tomodify the drive.

The operation of clutch unit 10 typically begins with rotational powerbeing supplied to input shaft 18. The rotation of input shaft 18 rotatesfan 58 to provide a flow of cooling air over clutch unit 10. Therotation of input shaft 18 also drives driving gear 42 of gear pump 40which in turn drives driven gear 44. The operation of gear pump 40 pumpshydraulic oil through outlet 140, through passage 144, through outlet146 and into passage 128 of valve block 120 if input shaft 18 is turningclockwise and pumps hydraulic oil through outlet 142, through passage148, through outlet 146 and into passage 128 of valve block 120 if inputshaft 18 is turning counterclockwise. Because solenoid valve 124 isclosed, the pressurized fluid delivered to passage 128 will eventuallyopen pressure relief valve 122 and the hydraulic oil will return tochamber 30 through outlet passage 130. The hydraulic fluid returnedthrough outlet passage 130 will flow into chamber 30 and lubricate themoving components within chamber 30. The rotation of input shaft 18 willalso drive driving friction plates 90 but this rotational motion willnot be transferred to driven friction plates 92 because piston 66 isbiased to the right as shown in FIG. 1 by coil springs 80 to release theclamping load between friction plates 90 and 92.

When it is desired to engage clutch unit 10, solenoid valve 124 isactuated or opened to open communication between passage 128 and outletpassage 132. Because solenoid valve 124 is open, the pressurized fluiddelivered to passage 128 will flow through outlet passage 132, throughfluid line 134, through passage 68 and into annular chamber 78. Thefluid pressure within annular chamber 78 will react against the load ofcoil springs 80 and move piston 66 to the left as shown in FIG. 1 toapply a clamping load between friction plates 90 and 92. With theclamping load applied, clutch unit 10 is in the engaged position anddriving friction plates 90 will drive driven friction plates 92 torotate output shaft 20. The fluid pressure within chamber 78 will buildup until pressure relief valve 122 again opens to dump pressurizedhydraulic fluid back to chamber 30. Thus, the engagement pressurebetween friction disks 90 and 92 can be controlled by adjusting pressurerelief valve 122. The rotation of output shaft 20 also powerscentrifugal pump 110 to pump hydraulic oil from chamber 30 into cavity112 into axial passage 114 and through radial passages 116 to providecooling oil for the interface between friction disks 90 and 92. As longas solenoid valve 124 is open, clutch unit 10 will remain engaged withthe engagement pressure being determined by pressure relief valve 122.

With clutch unit 10 engaged, disengagement of clutch unit 10 isaccomplished by closing solenoid valve 124. Flow of pressurized fluidfrom passage 128 is as described above. In addition, the pressurizedfluid within annular chamber 78 is bled back to chamber 30 throughreturn passage 136. The closing of solenoid valve 124 puts outletpassage 132 and thus chamber 78 in communication with return passage136.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A bi-directional clutch unit comprising: a housing assembly definingan oil sump; an input shaft rotatably supported by said housingassembly; an output shaft rotatably supported by said housing assembly;a clutch disposed between said input shaft and said output shaft, saidclutch being selectively moveable between a disengaged condition wheresaid input shaft is rotatable with respect to said output shaft and anengaged condition where said input shaft is drivingly connected to saidoutput shaft, said clutch comprising a plurality of driving frictiondisks interleaved with a plurality of driven friction disks; and acentrifugal oil pump powered by said output shaft, said centrifugal oilpump being operable to pump oil from said sump to said plurality ofdriving and driven friction disks, said plurality of driven frictiondisks define an internal spline in engagement with an external splinedefined by said output shaft, said output shaft further defining anaxial fluid passage disposed radially inward from said plurality ofexternal splines, said oil pump being operable to pump oil from saidsump to said axial fluid passage, said output shaft further defining aplurality of radial fluid passages in communication with said axialfluid passage, in that once said output shaft is stationary from thedisengagement of said clutch, said oil pump only being operable to pumpoil from said sump to said axial fluid passage and from said sump tosaid plurality of radial fluid passages when said clutch unit isreengaged.
 2. The bi-directional clutch unit according to claim 1,wherein said oil pump is immersed in said oil.
 3. The bi-directionalclutch unit according to claim 2, wherein said plurality of drivenfriction disks define an internal spline in engagement with an externalspline defined by said output shaft.
 4. The bi-directional clutch unitaccording to claim 3, wherein said output shaft defines an axial fluidpassage disposed radially inward from said plurality of externalsplines, said oil pump being operable to pump oil from said sump to saidaxial fluid passage.
 5. The bi-directional clutch unit according toclaim 4, wherein said output shaft defines a plurality of radial fluidpassages in communication with said axial fluid passage, said oil pumpbeing operable to pump oil from said sump to said axial fluid passageand from said sump to said plurality of radial fluid passages.
 6. Thebi-directional clutch unit according to claim 1, further comprising anoil pump powered by said input shaft.
 7. The bi-directional clutch unitaccording to claim 6, wherein said plurality of driven friction disksdefine an internal spline in engagement with an external spline definedby said output shaft.
 8. The bi-directional clutch unit according toclaim 7, wherein said output shaft defines an axial fluid passagedisposed radially inward from said plurality of external splines, saidoil pump being operable to pump oil from said sump to said axial fluidpassage.
 9. The bi-directional clutch unit according to claim 8, whereinsaid output shaft defines a plurality of radial fluid passages incommunication with said axial fluid passage, said oil pump beingoperable to pump oil from said sump to said axial fluid passage and fromsaid sump to said plurality of radial fluid passages.